Altered states of consciousness induced by breathwork accompanied by music

Here is the direct link for the breathing technique:

http://journals.plos.org/plosone/article/asset?unique&id=inf...

> encouraged by the tempo of the music progressively increasing to the end of HVB

How does this part work? No real music does this so did they make their own for the study? Or do they select songs that change tempo subtley from one to the next?

They could have made their own, but it's really not that uncommon for music to slowly increase in tempo. Some styles of music use it more than others - for instance, ceremonial drumming might start out extremely slow and build to a frantic climax. But it's also fairly normal for musicians who are playing live, rather than to a click, to speed up when the music gets more intense.